PROJECT SUMMARY who inject drugs (PWID) are at high risk for serious but treatable and preventable medical consequences of their drug use, including HIV and Hepatitis C Virus (HCV) infections and fatal overdose. The current opioid crisis poses a threat for outbreaks of HIV among PWID, has resulted in increased incidence of HCV, and has led to dramatic increases in opioid overdose mortality. PWID need accessible medical treatment services for the consequences of their drug use. Syringe service programs (SSPs) are stigma-free settings that can provide PWID with healthcare services onsite or through close partnerships with local medical providers. In December 2015, the ban on Federal funding for SSPs was lifted. Since then the number of SSPs in the US has almost doubled, from 220 to approximately 430. Innovative models for delivering HIV and HCV care, HIV prevention (PrEP), and OUD medication at SSPs can expand PWID healthcare access, uptake and engagement, but they are not well described or evaluated systematically. Building on our previous studies of expanding HIV and HCV testing in substance use treatment programs, we propose to describe healthcare models that provide varying combinations of HIV, HCV, and opioid use disorder medication services onsite and off-site in the fast-growing SSP sector, and evaluate the feasibility of sustainably implementing them in different settings from the perspectives of the programs and their clients. Our specific aims in the next funding period include: 1) describing current models and recent trends of HIV and HCV care, PrEP, and OUD medication services in SSPs nationally; 2) assessing the feasibility of expanding SSP healthcare care models from SSP program perspectives; and 3) identifying drivers of preferences for different SSP healthcare models from SSP client perspectives. We will use a mixed-methods sequential approach by conducting two updated national SSP surveys to collect quantitative data and qualitative interviews with SSP program directors and staff in diverse settings, including SSPs that do and do not provide HIV, HCV, PrEP and OUD medication services onsite. Qualitative interviews will explore onsite versus off-site delivery options, costs, sustainability of services currently provided, and plans for future expansion in the context of local community needs and barriers. We will also conduct an innovative discrete choice experiment (DCE) survey with a geographically diverse sample of SSP clients to identify and quantify their relative preferences for attributes of HIV, HCV, PrEP and OUD medication services. Results will be disseminated to state and local policy makers, public health practitioners, and funding agencies. Simultaneously with completion of this research, we intend to contribute to and inform the development and initial testing of interventions that will assist SSPs in expanding HIV, HCV, PrEP and OUD medication services. Our findings about the feasibility of models and preferences for attributes will inform the implementation of services that will sustainably maximize uptake and engagement.